1. Field of the Invention
The invention relates to a vehicle communication method and a communication device and, more particularly, to a vehicle communication method and a communication device in which data transmitted from a plurality of communication devices provided in various portions of a vehicle via communication lines is stored into a record medium and the amount of communication data sent from each communication device is changed.
2. Description of the Related Art
A remote diagnostic system has been developed in which vehicle information obtained by ECUs (electronic control devices) provided in various portions of a vehicle are sent to a storage device via a communication network called in-vehicle LAN (Local Area Network), and if a failure occurs in the vehicle, communication between a communication module in the vehicle and a failure analysis center is performed to send necessary vehicle information from the storage device to the failure analysis center, and the failure analysis center performs analysis of the vehicle's failure.
Japanese Patent Application Laid-Open Publication No. 2005-22556 describes sending and storing vehicle information from various ECUs to a record medium in the vehicle, and sending gathered information to an external server in accordance with need for diagnosis of abnormality of the vehicle.
Japanese Patent Application Laid-Open Publication No. 2004-232498 describes sending vehicle information to a storage medium in accordance with cycles predetermined for the individual ECUs.
In a remote diagnostic system in which each ECU sends vehicle information needed for diagnosis periodically to a storage device, it often happens that during the course of narrowing down potential causes of the failure, there occurs a desire to change the kind of vehicle information acquired from a specific ECU, or a desire to change the sampling cycle regarding the vehicle information acquired.
For example, if the number of kinds of vehicle information acquired from a specific ECU increases and the data amount increases, or if the data amount increases due to a change of the sampling cycle, there is a need to reduce the data amount of vehicle information acquired from the other ECUs so as to avoid congestion of the in-vehicle LAN.
However, if there is an error in the recognition of the amount of data sent by each ECU, or if the timing of decreasing the amount of data sent from the other ECUs is later than the timing at which the amount of data sent from a specific ECU increases, a problem arises, that is, congestion occurs in the in-vehicle LAN, so that information needed by the ECUs for the vehicle control cannot be obtained, and thus the vehicle control is considerably affected.